Troubleshooting my killer ant

[tfarny]

I know there are more amp-specific forums out there, but the guys here are just so trustworthy and cool, so I'll try here.
My little Killer Ant 1/4 watt tube head died completely and utterly last week. Neither tube (both 12ax7) was lighting up, so I changed back to the originals - they lit up but still no sound, nada, not a pop or a hiss. Both fuses are fine. Power light comes on for what it's worth. Emailed the company, no response whatsoever. I'm hoping somebody here can help me troubleshoot a bit - obviously if an expensive part is blown I'll just give up, but I definitely want to keep this guy, it's been a lot of fun. I have a multimeter and the caps are self-draining.

 

[DangerousR6]

My Blue Voodoo did that very same thing here about a month ago. It just quit one day while playing, I had replaced the tubes to no avail. And even tried replacing the stanby switch, turns out I was on the right path. One of the resistors in the stanby circuitry had gone bad. Part costs a total of .95 cents, but the repair bill was $150..... :doh:

 

[Patrick from Davis]

Well if the tubes light up then power is flowing.  There are several winds in the power transformer, and you need to check all of them.  Well, at least one more.  The filaments are going so that is fine, but the high voltage part needs to be checked.  You need to find the rectifier diodes and check the voltage after them to ground.  This is generally called B+, and should be in the hundreds of volts.  Depends on the amp.  Also, hundreds of volts means be careful and don't kill yourself checking.  If that is still going, the voltage is 300 volts or higher, then we can move on to other points to check.  While you are in the amp looking, look for any components that look burned up, or solder joints that have lost their luster.  If you let the smoke out of the components the amp doesn't work.  If the solder joints are dull and crappy looking, you could just have a bad solder joint that needs to be reflowed.

Before going further into the trouble checking, start there.  Also, note if it makes any noise when turning it on from standby, or nothing.  Does the output tranny smell at all?  The power tube should goto the output tube then the tranny then the connection for the speaker (4,8,16 ohm jacks)  Start with the easy stuff and move on.  If you know of a wiring diagram or schematic, this will really help narrow down the search for problems.  Good luck.
Patrick

 

[mayfly]

Another thing to test is if the o/p transformer is getting hot.  Also, sometimes with modern designs there is a fuse in the B+ line going to the o/p transformer - this may have blown.

Do you have any photos of the inside of the chassis for us to see?

 

[DangerousR6]

Another thing to test is if the o/p transformer is getting hot.  Also, sometimes with modern designs there is a fuse in the B+ line going to the o/p transformer - this may have blown.

Do you have any photos of the inside of the chassis for us to see?

That would be a slo-blo fuse wouldn't it?

 

[tfarny]

Well that is odd - took it apart to take a pic for you guys, then stuck the tube back in to give it one last go, and now it's fine! I have no explanation. Sorry for wasting your time. Here's the circuit in case you're curious - and this little guy is heaps of fun for the price of one pedal.

 

[Patrick from Davis]

I would grab the shop vac and vacuum out the insides.  From what you describe, the events, it sounds like something was making a short.  Clean it out and hopefully it never happens again.  Either that, or a bad solder joint that gets moved and makes contact and then doesn't.  Check the tube sockets solder joints just in case, that would be the place I'd look if my amp was behaving like that.  Most likely it will work fine now, but it never hurts to check everything while all of the info is fresh in your mind.
Patrick

 

[GoDrex]

I read something about there being some issue with BH amps... if I can find it I'll post again...


edit:

could it be the input jack? opening it up may have moved something...

ok here's the thing I read:

http://www.seymourduncan.com/forum/showthread.php?t=165368

 

[mayfly]

Another thing to test is if the o/p transformer is getting hot.  Also, sometimes with modern designs there is a fuse in the B+ line going to the o/p transformer - this may have blown.

Do you have any photos of the inside of the chassis for us to see?

That would be a slo-blo fuse wouldn't it?

actually usually it's a fast blow.  There is little in-rush current into the o/p transformer and you want the fast protection.  The mains fuse on the other hand has to be slow blow because there is considerable in-rush current to charge the power supply capacitors.

 

[tfarny]

I actually have a scratchy input jack on the 5watter, it annoys the hell out of me. Sprayed contact cleaner, it's a little better but needs to be replaced. I love the sound of both of them though, still these are just more reasons to go ahead and get my ceriatone....